Construction of polymer coated core–shell magnetic mesoporous silica nanoparticles with triple responsive drug delivery

Multi-responsive drug delivery systems are playing a very important role in nanomedicine, as they can feature as smart carriers releasing their payload on demand. In this study, magnetic, reductive and thermo triple-responsive nanocarriers based on core–shell magnetic mesoporous silica nanoparticles (MMSNPs) modified with a thermo responsive polymer poly(N-isopropylacrylamide) (PNIPAAm) have been developed. Photoinduced electron/energy transfer-reversible addition fragmentation chain transfer (PET-RAFT) polymerization, mediated by a ruthenium-based photoredox Ru(bpy)3Cl2 catalyst was used to graft PNIPAAm onto MMSNPs. A series of characterization and testing techniques were applied to confirm the structures of the synthesized nanocarriers to assess their efficiency as drug delivery systems. Doxorubicin (DOX) was easily encapsulated into the nanocarriers with a high loading capacity, and quickly released in response to the triple-responsive systems. The MMSNPs remained intact in all synthetic steps, during the loading of the drug and the in vitro release tests. Thus, these multi responsive polymer grafted Fe3O4-capped-MSN models are not only magnetically guided, but also represent a promising candidate in the formulation of targeted delivery of therapeutic agents to temperature and more reductive environment tissues, such as tumors and inflammatory sites.